The invention pertains to a thick materials pump in keeping with the preamble of claim 1.
The thick materials to be conveyed by the pump of the invention can be of varied composition, while, as a general rule, the given thick material being conveyed represents a mixture of different materials. Generally, these are mushy masses with a more or less great proportion of water, e.g., sewage sludges, mortars, or the like. In particular, the invention pertains to pumps for concrete, by means of which the liquefied mixture consisting essentially of sand, cement, additives, and water must be pumped over relatively great distances and differences in height.
The thick materials pump of the invention operates with feed cylinders, in which the pistons move back and forth and, during the backward stroke, load the cylinder with the thick material usually drawn in through the slide housing from a filling container, while, during the forward stroke, the slide forces the thick material into a feed conduit affixed to the frame. In keeping with the invention, two feed cylinders always work in tandem in such a way that one of the cylinders is being filled while the other is being emptied into the feed conduit, so that the intake and delivery strokes of the two pistons overlap. Accordingly, the invention can be adapted to more than a single pair of cylinders when a temporally closer overlapping of the feed strokes is desired.
Regulation of the feed and intake flow is accomplished by the slide, which has a branch channel for each feed cylinder, which, during the feed stroke, communicatively connects the cylinder with a central channel leading to the feed conduit, while the slide simultaneously frees the aperture of the cylinder with the intake piston, so that the incoming thick material flows past the slide and into said cylinder. As a general rule, when the thick materials pump has more than one pair of feed cylinders, additional branch channels must be provided for each added feed cylinder. The invention is described in greater detail below in terms of its preferred embodiment form, which is designed as a two-cylinder pump for thick materials.
It must be initially pointed out, however, that in all embodiments of the thick materials pump of the invention the openings of the branch channels in the slide, which communicate with their respective cylinders, must seal against the wall of a slide housing, so that, on the one hand, the flow of thick material under the pressure of the feed piston does not completely or even partially spill into the intake cylinder during its filling with thick material, and on the other hand, the thick material cannot flow back into the filling container during the intake. Consequently, a certain sequence of the movements of the slide must be synchronized with the movements of the pistons in the cylinders, which is also a part of the invention, just as is the possibility, in the case of many thick materials pumps of this type, of feeding the thick material from the feed conduit into the slide housing communicating with the filling container by reversing the sequence.
These general features described above characterize thick materials pumps, which are generally expected to be capable, with simple construction and despite their complicated method of operation and their stresses during the feed operation, especially over great delivery distances and heights, of operating without excessive disruption due to wear or failure of functionally essential components and, particularly, of providing continuous feeding of the thick materials to the maximum extent possible. This problem is fundamental to the invention.
A pump for thick materials of the type described in the introduction is known (German Patent (OLS) No. 2,721,678), which has a slide in the form of a V-shaped, bifurcated pipe, in which the branch channels from the tines of a fork and the longitudinal axis of the central tube is the geometrical axis, on which the slide pivots when the pump is in operation. The forked tube is then formed by the separation of the parallel or aligned feed cylinders in the embodiment form of a two-cylinder pump for thick materials. The bifurcated design of the slide is also suitable for four-cylinder pumps for thick materials, while the pairs of feed cylinders must then be aligned and two cylinders must act simultaneously as delivery cylinders. Regardless of the number of feed cylinders, the free ends of the branch channels are curved, while, in the embodiment as a two-cylinder pump for thick materials, one opening of one of the two cylinders always closes against one of the two sealing control surfaces, while the other provides the connection with the feed cylinder. Accordingly, these sealing control surfaces are flat and therefor located at the base of a filling container.
The stresses on the slide are disproportionately great during operation and intensify with increasing feed length and height. This is due to the reaction forces developed in the slide during the feeding of the thick material. With each stroke of a feed piston the two openings of the branch channels are subjected to the feed pressure. From the feed pressure and the areas of the interior cross section of the branch channels, reaction forces develop in both branch channels, which cause the slide to lift away from the sealing control surface and the aperture of the feed cylinder. It is true that these forces are partially compensated by forces developed from the interior cross-sectional area of the central channel and the feed-channel pressure. This is the force that must be overcome by the feeding. Consequently, there remains considerably residual force, which produces a rift at the openings of the branch channels, which cannot be tolerated if the aforementioned short circuiting of the feed flows is to be avoided. This dictates disproportionately heavy bearings for the pivoting slide and the shaft powering the slide. Nevertheless, premature wear of these essential components cannot be ruled out.
The fundamental objective of the invention is avoidance of these shortcomings and attainment of results, which favorably affect the problem cited in the introduction.